Prior art devices have been designed to provide a high velocity jet for exhausting atmosphere and other gases, as described in, for example, U.S. Pat. No. 4,806,076, issued to Andrews, and U.S. Pat. No. 5,439,349, issued to Kupferberg. These exhaust fans are typically mounted on the roof areas of buildings and are used to carry exhaust gases as high as possible above the roof line of the building so as to ensure an effective final dilution of the gases within the greatest possible volume of ambient air and their dispersal over a large area with maximum dilution. The fan in U.S. Pat. No. 4,806,076 has a nozzle in which two converging flow paths are defined by two respective passageways. The walls forming these passageways are shaped as sectors of conical sections. A wind band is provided at one end of the two passages at the outlets thereof to provide an entrainment of fresh air to mix with the gases exhausting from the two passageways.
Conventional exhaust fans for moving large volumes of air often generate high levels of noise which is undesirable. As a result, a wide variety of fan silencing equipment has been proposed to absorb fan noise, thereby reducing fan noise to an acceptable level. However, conventional silencers are used at the fan portion of the device, and do not control noise at the nozzle or outlet portion. These conventional silencers are undesirable for several reasons, including because they lead to an increase in the overall height of the fan device and they are limited to a relatively low air distribution velocity (on the order of less than about 3000 feet per minute) in which they are effective (i.e., provide maximum attenuation without themselves generating any significant additional noise). Therefore, a need exists for a device that controls noise at the nozzle or outlet portion to reduce the height of a fan or other device and provide a relatively high air distribution velocity, without adding significantly to system pressure.